2001001891991 has 4 divisors (see below), whose sum is σ = 2001011248272. Its totient is φ = 2000992535712.

The previous prime is 2001001891961. The next prime is 2001001892023. The reversal of 2001001891991 is 1991981001002.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2001001891991 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2001001891961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4349651 + ... + 4787636.

It is an arithmetic number, because the mean of its divisors is an integer number (500252812068).

Almost surely, 2^{2001001891991} is an apocalyptic number.

2001001891991 is a deficient number, since it is larger than the sum of its proper divisors (9356281).

2001001891991 is an equidigital number, since it uses as much as digits as its factorization.

2001001891991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9356280.

The product of its (nonzero) digits is 11664, while the sum is 41.

Adding to 2001001891991 its reverse (1991981001002), we get a palindrome (3992982892993).

The spelling of 2001001891991 in words is "two trillion, one billion, one million, eight hundred ninety-one thousand, nine hundred ninety-one".